The NASA Deep Space Network hosts three complexes worldwide for spacecrafts tracking. The Spanish complex,
the Madrid Deep Space Communications Complex (MDSCC), operates a set of highly sensitive antennas, which
are used for Host Country Radio Astronomy (HCRA) during a percentage of their operational time. We have
designed, developed and built a wideband backend for HCRA in MDSCC, which greatly improves its available facilities,
and opens new scientic cases to be tackled. The backend is able to sample up to 6 GHz of instantaneous
bandwidth, in the frequency range from 18 to 50 GHz, using two dierent antennas. An intermediate-frequency
(IF) processor downconverts the two-polarization signals to four base-band channels of 1.5 GHz width. Digitalisation
is done through a set of FPGA-based FFT spectrometers, which can provide spectral resolutions from 7 to
200 kHz, and spectral coverages from 100MHz to 1.5 GHz each. This new facility enables HCRA to aord new
scientic projects, such as extragalactic radio astronomy and spectral surveys; at the same time, the available
time for HC is greatly optimized. It was necessary the development of dedicated software for spectra acquisition
and control of the equipment, and also the upgrading of the existing observing programs. Once end-to-end
assembled, the whole backend was tested through a set of commissioning observations. In this contribution
the main features of the new backend are described, including the IF processor, the FFT spectrometer and the
developed software. Some astronomical results are also included.